Electroluminescent device



J MATARESE ELECTROLUMINESCENT DEVICE Dec. 12, 1961 Filed June 11, 1959 CL www E A 11 31 11 yd m msi Y uk N VQQ SG. US .n v H vmmkw N ...tE Em Qm SQ E. Mmmm vn um. MSE QQM Smm .P2

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(d L 3m FF 42 @WF1/746 (e) l l I I M0075@ (f) I l /NPUT 52 n/F 30 2ND unser l/BE 30 3RD 721/2657 ATTORNEY l I TUBI-'30 4m TARGET United States Patent O1 3,013,183 ELECTROLUh/INESCENT DEVICE John Matarese, Bronx, N.Y., assigner to Sylvania Electric Products Inc., a corporation of Delaware Filed June 11, 1959, Ser. No. 819,638

2 Claims. (Cl. 315-169) My invention is directed toward electroluminescent display devices.

One type of electroluminescent display device, known as a crossed grid electroluminescent panel, includes an electroluminescent layer. A first set of parallel separate electrodes is secured to one surface of this layer, and a second set of parallel separate electrodes is secured to the opposite surface of the layer. The two sets of electrodes extend in non-parallel directions which, conventionally, are perpendicular to each other.

When a suitable voltage is applied between a selected first set electrode and a selected second set electrode, the portion of the electroluminescent layer subtended therebetween (defined asa cell) will luminesce, the light output increasing monotonically as the magnitude of the applied voltage increases. Through the use of suitable switching techniques, this voltage can be applied between each first set electrode-second set electrode pair in turn, thus successively energizing each cell in turn; the resultant effect is analogous to a cathode ray tube scanning operation.

At very high switching speeds, the time period available for the excitation of each cell is very short. Alternating voltages are normally employed, at relatively low switching speeds, to excite crossed grid electroluminescent panels. However, as the switching speed is increased, the frequency required for alternating voltage excitation becomes extremely high, particularly when the electroluminescent panel to be used has a large number of cells.

I have invented a new type of switching system for use with a crossed grid electroluminescent panel which does not employ alternating voltage excitation. My system can be used with electroluminescent panels having a large number of cells and can be operated at very high switching speeds.

In accordance with the principles of my invention, I provide an electroluminescent crossed grid panel cornprising an electroluminescent layer, a first set of parallel separate electrodes extending in a first direction and secured to one surface of this layer, and a second set of parallel separate electrodes extending in a second and non-parallel direction and secured to the opposite surface of said layer.

A complete pulse train, having a fixed recurrence frequency and containing a plurality of discrete pulses equal in number of the number of electrodes in the second set, is supplied with the same timing and duration to each of the first set electrodes in turn. At the same time, a separate pulse is supplied to each second set electrodes in turn, this process of supplying separate pulses being continued until the entire pulse train has been successively supplied to each of the first set electrodes. Each separate pulse is in time coincidence with the corresponding pulse in the corresponding pulse train. The polarity of the pulses in the pulse train is opposite to that of the separate pulses.

Under these conditions, each electroluminescent cell will be energized in sequence. The duration of each separate pulse as well as the duration of each pulse in the pulse train is so adjusted that each energized cell is deenergized (by the removal of all excitation pulses) prior to excitation of the next cell. (If the pulse duration is not so adjusted, then one or both excitation pulses I will be applied to more than one cell at the same time,

and spurious light emission will ensue.)

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An illustrative embodiment of my invention will now be described in detail with reference to the accompanying drawings wherein:

FIG. l illustrates one embodiment of my invention; and

FIGS. 2, 3 and 4 are illustrative waveforms of signals utilized in the embodiment of FIG. l.

Referring now to FIG. l, the output of a free running symmetrical multivibrator 10 is coupled through a first differentiation network 12 to the input of a first fiip-flop 14. The output of fiip-flop 14 is connected through a second differentiation network 16 to the input of a second liip-iiop 18.

Flip-flop 18 has two output terminals 20 and 22 which, in turn, are connected through a third differentiation network 24 to the control input terminals 26 and 28 of a first beam switching tube 30. This first tube has ten targets (anodes) 32 which are each coupled to a corre sponding vertical electrode 34 of an electroluminescent crossed-grid panel. (Vertical electrodes 34 and horizontal electrodes 36 have been shown in the drawing.

' The electroluminescent layer which in an actual panel is subtended between these horizontal and vertical'electrodes has been omitted from the drawing for ease in illustration.)

The last target 32 of tube 30 is connected to the input of aV buffer amplifier 38. The output of amplifier 38 is coupled through a fourth differentiation network 40 to the input of a third flip-flop 42. Flip-flop 42 has two output terminals 44 and 46 which, in turn, are connected through a fifth differentiation network 48 to the control input terminals 50 and 52 of a second beam switching tube 54. Tube 54 has ten targets Ywhich are each coupled to a corresponding vertical electrode 36 of the electroluminescent panel. 30 and hence is shown as a block in FIG. l.)

Tubes 30 and 54 are tubes of known type and,` for.

example, can be magnetron beam switching tubes of the type commercially designated as 6 700.

The operation of thesystem of FIG. 1 will nowfbe,r4 explained with reference to the waveforms of`FIGS. 2 3,

and 4. f

`Multifvibrator 10 produces rectangular-'shaped pulses, l

(IFIG. 2a) at a fixed recurrence frequency, for example, 200 kilocycles per second. These pulses are differentiated (FIG. 2b) and then supplied to the input of flip-flop 14. Flip-flop 14 responds only to differentiated pulses of negative polarity; as a result flip-flop 14 yields at its output rectangular shaped pulses (FIG. 2c) at one half of the Y frequency of multivibrator 10, i.e. kilocycles per second. The pulses produced by flip-flop 14 are differentiated (FIG. 2d) and then supplied to the input of flip-flop 16.

Flip-flop 16 responds only to negative pulses, and yields at its outputs 20 and 22 rectangular shaped pulses (FIGS. 2e and 2f) which have opposite instantaneous polarities. The recurrence frequency of these pulses is again halved to 50 kilocycles per second.

These 50 kilocycle pulses are differentiated (FIGS. 2g w i and 2h) and are then supplied to the control inputs 26 and 28 of the beam switching tube 32. This tube operates in conventional manner, the electron beam within the tube being advanced from one target to the next each time a negative pulse is delivered to either of inputs 26 and 28. The electron beam of tube 30 is therefore stepped at a 100 kilocycle rate; i.e. the beam steps from one target (Tube 54'is identical with tube.

The pulses from the `buffer amplifier are differentiated (FIG. 3b) and are then supplied to flip-flop 42. Fliptlop 42 responds only to negative pulses. It yields at its outputs '44 and 46 two rectangular pulses of opposite instantaneous polarity (FIGS. 3c and 3d). The recurrence frequency of these pulses is halved to 5 kilooycles per second.

These 5 kilocycle pulses are differentiated (FIG. 3e and 3b) and then are supplied to the control inputs 50 and S2 of the second -beam switching tube S4. Consequently, the electron beam within tube 54 is stepped at a l0 kilocycle rate.

In this manner, an electroluminescent crossed grid panel containing ten vertical and ten horizontal electrodes and thus containing one hundred electroluminescent cells can be completely scanned in a period of 1000 microseconds. It will be apparent that in the system described, a pulse train of ten pulses is applied to each horizontal electrode in turn. Further, in the period when this train is applied to any one horizontal electrode, a separate pulse is applied to each of the ten vertical electrodes in sequence, each separate pulse being supplied in time coincidence with the corresponding pulse in the pulse train.

Illustrative waveforms of the separate pulses and the pulse train, as utilized for example in actuating the electrode pairs respectively constituted by each of the second, third and fourth vertical electrodes 34 and the rst horizontal electrode 36, are shown in FIG. 4. It will be seen that, during excitation of any electrode pair, the pulse voltage on the vertical electrode rst decreases then increases, while the pulse voltage on the horizontal electrode iirst increases then decreases. Hence, the pulses applied to t-hese electrodes have instantaneous opposed polarities.

What is claimed is:

l. An electroluminescent display system comprising an electroluminescent panel having an electroluminescent layer, a first set of N different parallel electrodes secured to one surface of said layer and a second set of M different parallel electrodes secured to the opposite surface of said layer, said first and second electrode sets being mutually perpendicular, whereby said panel contains MN electroluminescent cells; first means to supply an entire pulse train to one of the first set electrodes and thereafter to supply said entire train successively to each of the remaining `first set electrodes in timed sequence, said train containing M different equidistantly spaced pulses of like polarity; and second means to supply a separate pulse to each of said second set electrodes and to repeat this process until said pulse train has been supplied to each of said first set electrodes, eac'n separate pulse being opposed in instantaneous polarity of the pulses of said train and being in time coincidence with the corresponding pulse in the corresponding pulse train whereby each of said electroluminescent cells is excited in sequence, there being MN separate pulses required to complete the cell excitation sequence.

2. An electroluminescent display system comprising an electroluminescent panel having an electroluminescent layer, a irst set of N diierent parallel electrodes secured to one surface of said layer and a second set of M different parallel electrodes secured to the opposite surface of said layer, said first andsecond electrodes sets being mutually perpendicular, whereby said panel contains MN electroluminescent cells; first means to supply an entire pulse train to one of the first set electrodes and thereafter to supply said entire train successively to each of the remaining first set electrodes in timed sequence, said train containing M different equidistantly spaced pulses of like polarity; and second means to supply a separate pulse to each of said second set electrodes and to repeat this process until said pulse train has been supplied to each of said first set electro-des, each separate pulse being opposed in instantaneous polarity to the pulses of said train and being in time coincidence with the corresponding pulse in the corresponding pulse train whereby each of said electroluminescent cells is energized in sequence, the pulse duration of each separatc pulse and each pulse in the pulse train having values at which each energized cell is deenergized prior to excitation of the next cell.

References Cited in the tile of this patent UNITED STATES PATENTS 2,313,286 Okolicsanyi Mar. 9, 1943 2,608,674 Depp Aug. 26, 1952 2,857,550 Cola Oct. 21, 1958 2,866,922 Matarese Dec. 30, 1958 2,876,381 Moss Mar. 3, 1959 2,877,376 Orthuber Mar. l0, 1959 

